Apparatus for adjusting tip clearance in fluid flow machines

ABSTRACT

A fluid flow machine of the type wherein adjacent rows of rotor blading rotate between adjacent rows of blading carried by the stator and wherein a ring formed from arcuate intermediate pieces fitted to the stator blading carrier intermediate adjacent rows of stator blading functions as a heat storage member and also forms a space separate from the flow passage for cooling stator blading carrier. The inner periphery of the ring of intermediate pieces establishes a running clearance with the tips of the rotor blading and this clearance is made adjustable by the insertion of packing strips between key portions formed on the intermediate pieces and the walls of circular grooves formed in the stator blading carrier in which these key portions are secured.

United States Patent [1 1 Sidler I APPARATUS FOR ADJUSTING TIP CLEARANCE IN FLUID FLOW MACHINES [75] Inventor: Erwin Sidler, Baden, Switzerland [73] Assignee: Brown Boveri & Company Limited,

Baden, Switzerland [22] Filed: Oct. 17, 1972 [21] Appl. No.: 298,235

[30] Foreign Application Priority Data Nov. 10, 1971 Switzerland 16255/71 [52] U.S.Cl 415/199 R,4l5/217,4l5/218 [56] References Cited UNITED STATES PATENTS 2,722,373 11/1955 Ledwith et al 415/218 2,749,026 6/1956 Hasbrouck et a1 415/218 FOREIGN PATENTS OR APPLICATIONS 468,847 10/1950 Canada 415/218 Feb. 5, 1974 1,162,384 2/1964 Germany 415/136 Primary Examiner-Henry Raduazo Attorney, Agent, or FirmRalph E. Parker et a1.

[ ABSTRACT A fluid flow machine of the type wherein adjacent rows of rotor blading rotate between adjacent rows of blading carried by the stator and wherein a ring formed from arcuate intermediate pieces fitted to the stator blading carrier intermediate adjacent rows of stator blading functions as a heat storage member and also forms a space separate from the flow passage for cooling stator blading carrier. The inner periphery of the ring of intermediate pieces establishes a running clearance with the tips of the rotor blading and this clearance is made adjustable by the insertion of packing strips between key portions formed on the intermediate pieces and the walls of circular grooves formed in the stator blading carrier in which these key portions are secured.

2 Claims, 1 Drawing Figure from the flow passage for cooling the stator blade carrier.

With fluid flow machines of this kind, the procedure for adjusting the tip clearance has usually been that the fully assembled rotor is laid in the casing, also fully assembled, the surfaces around the circumference between the blade rows being lined with strips of lead. When the rotor is placed in position, the blade ends are pressed into the lead strips. When the rotor is removed from the casing the actual clearances between the blade ends and the surface of the casing can be determined from the remaining deformation of the lead strips. On the basis of measurements the rotors and/or blade ends are then machined again, i.e., the blade tips are returned or reground.

Another possible-way of correcting the clearance is to rework the casing or the stator blade carrier. With present manufacturing techniques, reworking constitutes the only method of influencing the top clearance because otherwise, owing to the wide variations brought about by the many tolerances of the individual parts, it is not possible to ensure the required efficiency.

Furthermore, reworking not only requires a very large amount of time but also unusually extensive use of complex, and hence expensive, machine tools. Also, the structure of the components which have to be matched to each other makes it difficult to measure their geometrical form exactly.

As a result, adequate precision can be achieved only by repeated measurement and reworking, the only method which can beused being that described above.

The primary object of the present invention is therefore to avoid the time and expense of reworking and repeated measurement.

This objective is achieved in that the intermediate pieces provided between the rows of stator blading are provided with keys located in circumferential grooves, undercut on at least one side, in the stator blade carrier, the groove containing not only the key but also packing strips of such dimensions that the clearance along the blade tip is virtually uniform and the inclination of the surface of rotation of the rotor is equal to that of the surface formed by the intermediate pieces.

The technical improvement offered by the invention lies not only in the fact that the packing strips can easily be manipulated, but also that the tip clearance can be matched in optimum manner to each individual row of rotor blades. In this way the efficiency can be improved because windage losses can be significantly reduced by decreasing the actual clearance.

A further advantage is attained when materials are used for the stator and rotor blades which, because the blades have been hardened or provided with a protective coating, do not allow reworking. Particularly in the case of inchromized rotor blades the surface and structure must not be disturbed at any point. This advantage is also important when plastics materials with protective coatings are used.

This advantage, however, is not restricted to the blades themselves, but is also of great significance in the case of fluid flow machines in which corrosive media flow or are conveyed through the flow channel. Following the concept of the invention, the intermediate pieces and the stator blades also need no reworking and so the protective coating required on all parts under such circumstances is not disturbed in any way.

The invention will now be explained in more detail with reference to the drawing, which shows a section from the flow passage of a gas turbine.

The rotor l is fitted with moving blades 2 which are located in slots around the shaft and secured by means of a root fixing. The stator blade carrier 3 is mounted I in theouter casing and in addition to the circumferential grooves 5 in which the stator blades 4 are fixed, incorporates further circumferential grooves 6. A ring formed from arcuate intermediate pieces 7 is anchored in the circumferential grooves 6 by means of key 8 thereon so that the intermediate pieces 7 form a partition between the flow passage 9 existing between the rotor and stator blading 2,4 and a circumferential cooling-gas space 10 located radially outward of the ring of intermediate pieces 7.

The individual intermediate pieces 7 include manufacturing tolerances, in the same way as the other components, such as rotor blades 2, the shaft, stator blade carrier 3, etc. These tolerances must be compensated by tip clearance a, the purpose of which is also to compensate thermal expansion. The circumferential grooves 6 are undercut on one side, providing a circumferential recess 11 into which the packing strips 12 and 12 are inserted. The thickness of the packing strips 12 and 12 is made such that the inclination a of the conical surface formed by the inner periphery of the ring of intermediate pieces 7 is equal to the inclination a of the adjacent rotor blade tip. This also has the effect of making clearance a uniform along the end of the blade profile.

By varying the thickness of the packing strips 12 and 12' around the circumference it is possible to match the surface of the flow passage to the surface of rotation of the rotor blades. In this way account can also be taken of any sag in the rotor without incurring added expense.

When using packing strips 12 on gas turbines in conjunction with intermediate pieces it has been found that savings in losses of approximately 1,000 kW can be achieved, since the manufacturing tolerances of the casing can be fully compensated and those of the rotor can at least be reduced. Under favorable circumstances, therefore, it is possible to achieve the ideal tip clearance, i.e., the smallest possible clearance consistent with thermal expansion.

I claim:

l. A fluid flow machine comprising a rotor provided with adjacent rows of blading rotatable between adjacent rows of blading carried by a stator, a ring formed from arcuate pieces fitted to the stator blading carrier intermediate adjacent rows of the stator blading, the inner periphery of said ring of arcuate intermediate pieces being inclined in the axial direction of the rotor and confronting an inclined peripheral surface of rotasaid arcuate intermediate pieces, said packing strips being dimensioned such that said running clearance along the blade tip is uniform and the inclination of the peripheral surface of rotation formed by the tips of said rotor blading is equal to that of the inner periphery of said ring of arcuate intermediate pieces.

2. A fluid flow machine as defined in claim 1 wherein said circumferential grooves are undercut to receive said packing strips.

UNITEQSTATES 'IVPATEN'II" OFFICE C TE OF CORRECTION Patent Q- g qogqq a d Februarv 5. 197

Inventor(s) Erwin Sidler It is certifieditha t errqrappearsin the above-identified patent and that said Letters Patent 'are hereby corrected as shown below:

Claim 1, line 15, after "and" insert:

1 4 means Signed and sealed this 17th day of September 1974.

(SEAL) Attest:

MCCOY M. GIBSON JR. v v c. MARSHALL DANN Commissioner of Patents Attesting Officer Y USCOMM-DC 60376-P69 U.S. GOVERNMENT PRINTING OFFICE: (969 0-366-334,

FORM PO-1050 (10-69) 

1. A fluid flow machine comprising a rotor provided with adjacent rows of blading rotatable between adjacent rows of blading carried by a stator, a ring formed from arcuate pieces fitted to the stator blading carrier intermediate adjacent rows of the stator blading, the inner periphery of said ring of arcuate intermediate pieces being incLined in the axial direction of the rotor and confronting an inclined peripheral surface of rotation formed by the tips of the rotor blading to establish a running clearance therebetween, each said arcuate intermediate piece including a key portion formed at each side thereof and said key portions being received respectively in circumferential grooves provided in the stator blading carrier correlated to adjacent rows of the stator blading, and to adjust the clearance between the arcuate inclined ring pieces and the inclined peripheral surface of rotation formed by the blade tips, said means comprising packing strips placed in said grooves between the walls of the grooves and the key portions of said arcuate intermediate pieces, said packing strips being dimensioned such that said running clearance along the blade tip is uniform and the inclination of the peripheral surface of rotation formed by the tips of said rotor blading is equal to that of the inner periphery of said ring of arcuate intermediate pieces.
 2. A fluid flow machine as defined in claim 1 wherein said circumferential grooves are undercut to receive said packing strips. 